Problem: Cayden has several screws on a scale, and the scale reads $80.955\,\text{g}$. Cayden adds $1$ more screw, and the scale reads $84.81\,\text{g}$. What is the mass of the last screw Cayden adds?
Answer: New mass $-$ previous mass $=$ mass of the screw. $\begin{matrix} &&&&&\\ &{8}&4.&8&1&0\\ -&{8}&0.&9&5&5\\ \hline &{0}&3.&8&5&5\\ \end{matrix}$ ${80}-{80}={0}$ The screw massed $3.855\,\text{g}$.